Sustaining the activity of reforming catalysts



c. H. HOLDER Oct. 2, 1945.

SUSTAINING THE ACTIVITY OF REFORMING CATALYSTS Filed Nov. 12, 1943zwmmwwn J? LUQQQNR @N OW RQBQNPNW .J Nw WNWJOOU ..W`u NNN`SN RW W Q :w nW. NWQQQUN y ,2f k Il! Nm mm NJW. a .Allktmm Y .4 M. QM, NR wk; n\ .@HmA om w \\.NwNM0WH a N\v\ .\NN NPOLWQNN. Muvmbk Md a www@ Ll mlllll "Q eum nnnnnuLL A Nm 0m lauw v M om: m klo QWNV @bmg Nww m1 miuxowk/ mw.

M /z/WM 355? www 7 Patented-Oct. 2,- 1945 sUs'rAmlNc 'rmi Ac'rm'rr oFBanouma cA'rALrszrs clinton n. nouer. cantore. N. .1., manor to StandardOil Development Company, a corporation of Delaware Application November12,1943, Serial N0. 510,071 6 Claims. (Ul. 19E-450) The presentinventionrelates to improvements in the catalytic treatment ofhydrocarbon oils to produce aromatics, and more particularly it relatesto improvements resulting in maintaining the activity of catalysts, suchas dehydrogenation catalysts, on a high level of activity.

. A large number of commercial chemical process operations are todaycarried out in the presence of catalysts. v Of course, in all of theseproc'- esses the activity of the catalyst is a major consideration forinvariably the success of the process depends on maintaining thecatalyst, particularly in a continuous operation, at a high level ofactivity. Very few processes employing a catalyst can'be, conducted soas to produce 100 per cent yields of charged material. This isparticularly true in the catalytic treatment of petroleum oils. Thus,for example, in the catalytic cracking of gas oil to form gasoline, aprocess is considered to be operating Lsatisfactorily when the yieldsare of the order of i5-50% cracked gasoline based on the volume of gasoil charged. The same is true in the dehydrogenation of, say, butene togive butadiene, and is otherwise true in a'number of processes. Thedifiiculty of a great many of these processes, however, is that as thecatalyst becomes old in the process its activity tends to decline forone reason or another. For example, in the reforming of naphthas, eventhe best catalysts developed heretofore tend to lose activity which ismanifested in reduced yields of the desired product after the catalysthas passed through a large number of cycles, including theproductivephase and the necessary regeneration phase. For instance, a.study has been made of a reforming catalyst which, when freshly preparedand used, was adapted to catalyze the process so that 70 volume per centof toluene based on the methylcyclohexane fed to the process resulted asinitial yields, but after ve months in use the toluene yield was reducedto 56%, even though the operating conditions were uniform throughout thestandard run. It is believed obvious that anymethod or treatment of thecatalyst which would increase the toluene yield from the low gure givenwould be of the utmost importance, and my present invention has to dowith a treatment of catalysts which have lost activity, so 'as torestore atleast a part of that acivity.

While Ymy invention is of general applicability, I shall illustrate apreferred modication thereof in terms ofthe restoration of a reformingcataLvst and shall describe increasing the activity of a catalyst whichhas been decreased` byl continued use.

During the course of certain investigations, I observed that wheremolybdenum oxide catalysts supported on activated alumina. wherein themolybdenum oxide constituted 8 weight per cent of the total catalystmass, were used that hydrogen sulfide reacted with the white, highlyoxidized catalyst and formed a black material (presumably the sulfide)which in turn changed to a white color by oxidation in air. The reactionwhich occurred probably can berepresented as follows:

For sulfiding and for oxidation A 2MoSz+70z 2MoOa (white) +4802 Otherevidence obtained by X-ray analysis in-l dicated the presence of acompound consisting of molybdenum oxide and the catalyst carrier whenthe used low activity catalyst was examined. It was concluded that if anappreciable loss in the catalyst activity was due to a chemical compoundformation in-this manner, it might be possible to restore the activityof the used molybdenum oxide catalyst by first reacting the oxidecatalyst with hydrogen sulde and reoxidizing (as indicated above). Onthe other hand, it was felt that reactivation of the catalyst mightoccur due to a l change' in the surface characteristics, to give adehydrogenation.

preferred adsorption and hence a more efllcient In other words, theresulting oxide surface formed from the sulde might possess differentand desirable characteristics com-` pared to those after a normalregeneration and pretreatment. It should be explained, of course, thatin using the above catalyst in the reforming of naphthas, that duringthe reforming operation proper, tarry and coke-like deposits are formedon the catalyst which deposits necessitate discontinuing the reformingoperation and regenerating the catalyst by treating with anoxygen-containing gas at elevated temperatures.

In order to test the feasibility of the theory regarding the changesthat might take place in the catalyst during repeated use in cycles ofreforming and regeneration, four runs were made using a catalyst havingthe composition as set forth below, in which in three cases theregenerated oxidized catalyst was treated with an excess of HnS'and inthe other case the regenerated reduced catalyst was treated withHzS andin all cases the sulilded catalysts were reoxidized and kthen reduced atatmospheric pressure prior to starting the oil feed. The catalystemployed was typical of its type and consisted of 8.0 weight per cent M:supported on activated alumina (92%). The runs were carried out in a 1bbl./day pilot plant hydroformer 1 having adiabatically 1Hydroformin isan operation in which ttoleum oil, usually a napht nene-containing nahtha s treated at around 900 F. and a pressure ot a out 240 lha/squareinch auge using a catalyst and also usin added hydrogen. It di ers fromreformin in that add hydrogen is included in the charge to e reactionzone.

wound heating elements. The operating procedure maybe |broken down intothe following steps:

reactor I. The feed stock passes through the reactor under theconditions previously stated and is withdrawn through line I2, thencecooled in a cooler` I4, thence passed via line I5 into a high pressureseparator I8. In high pressure separator I8 the hydrogen orhydrogen-containing gas isl Example DirectionV Hrs..min. Step Conditionsof uw 4 hrs Reaction period 21M/sq. in. sa.. 0.65 v./v./hr., 2500 CF/Brecycle gas rate, 900 F. avg. catalyst Down,

temperature with approx. llOOPF. inlet temp. mins Recycle gas(regeneration Catalyst regenerated at 21M/Sq. In. sa. into recoverysystem using 50 CF ot Up.

- fumes or due gas) Purge. recycle gas/hL/C. F. of catalyst. 19 minsNitrogen purge Reactor purged to vent using 36 CF of nitrogen/hr./CF ofcatalyst Up. (Approx. mins.) Regeneration--. Catalyst regenerated at200#/sq. m. ga. with air using recycle ilue gas as diluent. Down.

Inlet temp. 800F., maximum catalyst temp. l100F. (Approx. 85 mina). Airrecycle After 0: appeared in reactor outlet stream air was admitted toreactor at same Down.

rate as in regeneration and recycled at rate of 1600 CF/hr. CF ofcatalyst. 5 mins Depressuxlng Reactor depressured to atmosphericpressure. Gas to vent Up. 1 hr Nitrogen purge Reactor purged to ventusing 36-93 C F of nItrogen/hrJCF oi catalyst Up. l hr... Hydrogensuliide purge.. Reactor purged to vent using 47 C F of hydrogensulldelhrJCF of cat. Cata- Up.

lyst at atm. pressure and approximately 010 F. 1 hr. Nitrogen purge-.Reactor purged to vent using 93 CF oinitrogen/hL/CF catalyst Up. 5 minsRepressuring-- Reactor repressured with nitrogen [scp in. ga Up,(Approx. 2 hrs.).. Reoxidation Catal st reoxidized at 200#/sq. in. ga. wth air using 1600 CF of recycle due Down. gas ./CF of catalyst asdiluent. Inlet temperature 800F., maximum catalyst temperature l100F.(Approx. 2 hrs.) Air recycle After O: appeared in reactor outlet streamair was continued to be admitted to Down.

reactrlattssme rate asin reoxidation and recycled at rate of i600CFlhrJCF o ca s Depressuring Reactor epressured to atmosphericcpressure. Gas to vent Up. Nitrogen purge Reactor purged to vent using36-93 F oi nitrogen r./CF of catalyst. Up. Recycle gas Purge pugedtatatmospheric pressure to vent us g 59 CF o! recycle gas/hn] Up.

o ca ys Repressuring Reactor repressured to 21M/sq. in. gauge usingrecycle ges Up. Reaction period Total cycle time approximately 15.5hours.`

The data obtained when using the modification of the normal operatingprocedure as disclosed herein is shown in the table below:

Eect of HzS treatment Br C D E F or compressor 32 through line 5 forfurther use. I A A portion of this hydrogen may be withdrawn 5a 54 55 56from the system through line 35. The fat oil, gctoifaatsar3: Nmaregt...Noma to that 1S the 011 containing the dissolved hydrohrlrl carbons, iswithdrawn from absorber 22 through Sith Hf' line 40 and passed into astripper 42 where it is His treatment iltilrl'isphec prelllig- N oneheated to remove dissolved gases by volatilization, Subsequent treatmentReoxidation plus normal re- Normal and these gases are Wthdra'wnoverhead through l cycle gas purge gig; line 45. Lean oil is withdrawnfrom the stripper Toluene yield, d .pex M5 62.0 63,2 5M through line 50,cooled ina cooler 52 and thence Prclp'ctanmne pt., i '51 sa so 52 s1 5eKfig?! E lossito recycle une for fur' 'Ihe raw product is removed asbottoms from s h i d h1 e1 n wreed.

ym Home wel based 9 met yey me 50' separator I8 through a line 60carrying a pres- It will be observed that the toluene yieldincreasedfrom 3 to 5.5 vol. percent as a result of the suliiding. Alsoit is shown that whether the sulilding is carried out over the oxidizedor the reduced form of the catalyst made very little difference.

In the accompanying drawing-'I havegshown diagrammaticahy, anapparatusin-,whlcha re- ':foiming operation may be carried out.

it contacts as it flows upwardly, a downward flow oil, such as anaphtha, introduced through line 25. 'I'he naphtha or .other petroleumoil serves to scrub out the methane and other hydrocarbon gaseswhereupon the hydrogen enriched gas is withdrawn through line 30 andpumped by pump sure reducing valve 62 and is discharged with the gas inline 45 into a stabilizer 'i0 from which the gases are recoveredoverhead through line 'I2 while the product is withdrawn through line13, cooledin a. cooler 14 and collected in a receiving drum 15.

Normally, the so-called hydroforming operation is a cyclic process, thatis to say, the operation justl now described as reforming is operatedfor a period of four hours and then the oil feed is discontinued toregenerate the catalyst because the catalyst acquires tarry or cokydeposits which of course reduce its activity; hence the catalystrequires the periodic regeneration referred to. l

In the foregoing description and in the accom panying drawing, I havenot shown all of the equipment that may be used lto facilitate theprocess. For instance, additional heat exchangers, iiow meters, andother engineering ex'- pedients can be used advantageously to improvethe operation.

I have previously described in detail the method of actually operatingthe regeneration and it will not be necessary at this point to repeat itin connection with the drawing. It will be sumcient to s'ay that duringregeneration of course the valve in oil feed line 3 is closed and thecatalyst is purged with inertgas from line l2. As previously stated,thisv purging gas is preferably flue gas at iirst followed by nitrogen.Thereafter the catalyst is treated with air from line Il and againpurged, then it is treated with hydrogen sulde from line 85, then it isoxidiitedA with air from Ill again, purged, repressured and placed onstream,

all of which regeneration procedure has beenl fully disclosedhereinbefore. It is pointed out that the regeneration fumes may bestored for further use by withdrawing them from the re actor throughline l2, thence passing them through line 92, thence through a cooler9|, thence through gas blower 96 and thence pass- ,Mjf'fg them tostorage drum |02 via line It is preferable to employ a purging gas whichcontains less than 6% free oxygen and the material therefore stored inIM should not contain more than this quantity of free oxygen. During theregeneration or purging, regeneration gas may be time, but also that theprocess can be modified to include the treatment with hydrogen sulde insitu, without any change from the currently existing catalysttemperature and without any changes in the pressure conditions. Insteadof using H28, I may use any volatile sulfide such as CS2. Also, aspreviously indicated, my process is applicable not only to the treatment0f the reforming catalysts but generally to the reactivation of metallicoxides whether they be used in naphtha reforming. dehydrogenation. oraromatization, or for any other purpose.I

' Numerous modifications of my invention will suggest themselves tothose who are familiar withv this art. What is claimed is:

1. A process of reforming naphthenic naphthas employing a catalystconsisting of an oxide of the VI group of the periodic system supportedon' an extending agent, which comprises contacting the naphtha atelevated temperatures and pressures with the catalyst in a reaction zoneduring the productive phase, discontinuing the ilow of naphtha to thereaction zone when the catalyst has become contaminated with deposits,purging the catalyst with an inert gas to remove volatile hydrocarbons,thereafter treating the catalyst with an oxygen-containing gas to causevcombustion of the contaminants on the catalyst, thereafter lowering thegas pressure in the reaction zona-purging the catalyst to removeoxygentheretrom,`treating the catalyst with a volatile sulfide to convert theVI group oxide to the sulfide, thereafter treating the catalyst with anoxygen-containing gas to. reoxidize the VI group suliide to the oxide,and

purging the catalyst to prepare it for the on-v stream phase of thecycle.

2. The method set forth in claim 1 in which the catalyst is treated withthe volatile. sulfide at pressures substantially lower than thoseemployed during the productive phase of the cycle.

3. The method set forth in claim 1 in which the volatile sulde is HnS.

4. The method set forth in,claim l in which the VI group oxide componentof the catalyst is molybdenum oxide.

. 5. The method set forth in claim 1 in lwhich added hydrogen is presentin the reaction sone during the productive phase for the purpose ofrepresslng carbonaceous deposition on the catalyst. 6. The method ofextending the active life of a VI group oxide catalyst employed inthereforming of naphthenic naphthas, which comprises regenerating thecatalyst fouled during the reforming operation by treatment with anoxygencontaining gas at; elevated temperatures and pressures whereby;`the vcontaminants are consumed by combustion, thereafter treating thecatalyst at a lower pressure with hydrogen sulfide whereby the VI groupoxide is converted to the corresponding sulfide, thereafter treating thesaid sulfide with oxygen to form the corresponding oxide and employingthe catalyst in this formin the productive phase.

CIENTO I N H. HOLDER.

